Using Astroquery to Find Data
Astroquery is a convenient, programmatic way to filter all of MAST holdings and retrieve the data files you want.
Using it effectively means understanding how the TESS data is represented in the MAST Observations database (also known as the Common Archive Observation Model, CAOM). All data at MAST is split into observations. Each of those observations have several data files associated with them. Once you have the observation ID you will be able to then request a list of data products. Thus most searches for MAST data through Astroquery require two filters, one on the observations level and one for the data products. These tables provide useful information about those fields you might use to do those queries. Please see the CAOM field list and data products fields for the full list of filters.
Observations
Filter | Field Name | How it is used for TESS |
---|---|---|
Observation ID | obs_id | FFIs: tess-s0001-4-2, where the 0001 is the sector, the 4 is the camera and 2 is the CCD Postage stamp: the name is based on the file name and encodes the TIC ID and Sector Information. |
Proposal ID | proposal_id | The Guest Investigator IDs are provided in this column. They are stored in a string with underscores separating them. e.g. G011183_G011132_G011048_G011250 |
Sector | sequence_number | Sector number is stored in this field as an integer. |
Data Product Type | dataproduct_type | FFI: "image" postage-stamp: "timeseries" |
Target Name | target_name | postage-stamp: The integer TIC ID is given. FFI: "TESS-FFI" is always the value. |
Data Products Filter
Filter | Field Name | How it is used for TESS Data |
---|---|---|
Minimum Recommended Product | mrp_only | When set to True you only get the most common data products. They are: postage-stamp: light curve files and target pixel files. FFI: There are no MRPs. |
Product Type | product_type | postage-stamp: "timeseries" FFI: "image" |
Description | description | Choices are":
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Data File Type | productSubGroupDescription |
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Common Problems when Using the MAST Portal
Problem | Solution |
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There are no FFIs to Download |
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I asked for a certain TIC ID, but it showed me products for a different part of the sky. | You must include the catalog name when you do a cone search, i.e. "TIC 100100827". Otherwise your number may match another catalog, like the K2 EPIC Catalog. |
I find no data when I do a cone search at the center of the Camera's Field of View. | The 4 CCDs per camera do not have continuous coverage. If you add a fairly large radius to your cone search, you will then overlap all four CCDs. For example, try Camera 4 by typing the following into the Portal's search box, 90.0042, -66.5647 r=2 d |